1. The Field of the Invention
This invention relates to damper control devices and more particularly to that class adapted to automatically operate the damper into an open position when the stack temperature exceeds a pre-determined level at a location immediately above the location of the damper.
2. Description of the Prior Art
The prior art abounds with mechanisms designed to control the positioning of vane type dampers mounted within a stack, used in combination with heating systems of diverse types, U.S. Pat. No. 2,179,120, issued to W. E. Firehammer on Nov. 7, 1939 teaches a solenoid operated damper which is actuated when the thermostat controlling the combustion cycling period of the heating system, calls for more heat. The damper is automatically closed when the heating system has elevated the ambient temperature surrounding the thermostat to the desired temperature, which in turn, causes the furnace to stop operating. U.S. Pat. No. 2,224,705, issued to G. E. Stringer, on Sept. 10, 1940, discloses a solenoid actuated vane type damper installed within the flue of a boiler which is operated into the open position when the ignition system of the boiler is energized. The damper is closed upon the de-energization of the ignition system. U.S. Pat. No. 2,344,925, issued to G. Den Besten Et Al on Feb. 9, 1944 illustrates a solenoid controlled vane type damper installed into the stack of a boiler which is operated into the open position when the flue pressure exceeds a pre-determined level and closes automatically when the flue pressure falls below another pre-determined level.
All of the aforementioned patents provide diverse means controlling the vane type damper other than sensing the temperature at a point immediately above the damper so as to conserve the energy stored in the stack during periods that the stack gasses are at a low temperature.